Wireless access points emit radio waves that are attenuated by furniture, doors, walls, windows, ceilings and floors. Consequently, good wireless network coverage in all areas of a building or a home can often not be ensured with a single wireless access point. For example, it is known that a wooden door attenuates a WiFi signal by 3 dB, which is half the signal strength, while a concrete wall or ceiling can attenuate a WiFi signal by as much as 10-15 dB (i.e., to about one eighth of the original signal). Attenuation is even more important in the presence of metal, such as tinted windows or steel reinforced concrete. Wireless network extenders, also called wireless repeaters (further referred to as wireless network extenders), can cover areas that are not or poorly covered by a single wireless access point and improve overall wireless network coverage. Wireless network extenders that wirelessly communicate with an access point are used when additional cabling is not wished or impossible.
In networking, the Media Access Control (MAC) is an ISO (International Organization for Standardization) level 2 or data link layer protocol that provides addressing and channel access control mechanisms that allow multiple client devices to communicate over a shared medium such as wired Ethernet or a wireless medium. The MAC address is a unique serial number assigned to a network interface of a network client device. A destination Internet Protocol (IP) address (ISO layer 3 or network layer) is resolved with the IPv4 Address Resolution Protocol (ARP) or with the IPv6 Neighbor Discovery Protocol to the MAC address of the destination network interface of a destination network client device. When a wireless network extender is configured to function as a network bridge, the wireless network covered by the access point and covered by the wireless network extender is seen as a single network from the access point of view, within a single network layer address space. The wireless network extender functions as a bidirectional relay for data communication between the wireless access point and wireless network client devices connected to the wireless network extender. The wireless network extender represents the wireless network client devices connected to it before the access point.
Inside a building, office or home, areas can exist that are covered both by the access point and the network extender. These areas are further referred to as areas of common coverage. As mentioned above, the network communication is based on a uniqueness of MAC addresses within the network. If the MAC address of a wireless network client device and that of its representation by the wireless network extender are the same, both the wireless network extender and the wireless network client device reply to messages from the access point in the common coverage areas. This causes data collisions that make data communication impossible between the wireless access point and the wireless network client device. Therefore, wireless network extenders employ MAC address translation. When the wireless network extender relays a data link layer message from a wireless network client device to the access point, it replaces the real MAC address of the wireless network client device in the message to a translated MAC address (TMAC). When the wireless network extender relays a data link layer message from the access point to a wireless network client device, it replaces the translated MAC address in the message by the real MAC address of the wireless network client device. This solves the problem of uniqueness of MAC addresses in the common coverage areas: any data link layer message transmitted from the wireless access point that has as a destination a wireless network client device that is connected to the wireless network extender is addressed to the translated MAC address of the destination wireless network client device and will continue to be relayed by the wireless network extender to the destination wireless network client device. Vice versa for data link messages that are transmitted from a wireless network client device to the access point and that are relayed by the wireless network extender.
While this solves the above discussed problem of communication loss in areas of common coverage of the access point and of the wireless network extender, the MAC address translation causes a problem of communication loss when the client device roams from the wireless network extender to the access point to a coverage area that is only covered by the access point and the wireless access point is configured to function as a bridge. In such a configuration, there is a single Dynamic Host Configuration Protocol (DHCP) server in the network. For communication on the network layer level (ISO level 3), the DHCP server attributes IP addresses to client devices of the network based on their MAC address. When a wireless network client device is ‘attached’ to the wireless network extender, its IP address allocation is based on its translated MAC address. When the wireless network client device roams to an area that is covered by the access point only, it will have to issue a DHCP request to obtain an IP address. In its DHCP request, the wireless network client device will provide its real MAC address. Instead of retrieving the IP address that was allocated to it before the roaming, the DHCP server will attribute a new IP address to the client device as the real MAC address of the wireless network client device is yet unknown to the DHCP server. As a consequence, any IP packets that are destined to the client device based on its previous IP address are lost, causing a communication disruption a.k.a. IP session discontinuity.
There is thus a need to improve prior techniques.